A NOVEL FLOW-THROUGH METHOD FOR TOXICITY ASSESSMENTS USING CERIODAPHNIA-DUBIA

Maintenance of chemical concentrations during toxicity tests is essent ial to determine the intrinsic toxicity of a material. For compounds t hat are sorptive, rapidly biodegraded, volatile or chemically labile, static and/or static renewal exposure strategies may result in large f luctuations in exposure concentrations over time, particularly for chr onic tests. This article describes the development and adequacy of a n ovel flow-through chronic toxicity test method for the cladoceran Ceri odaphnia dubia, using a rapidly biodegradable surfactant, dodecyl alky l sulfate (C(12)AS) as a model compound. Organisms were exposed to C(1 2)AS in polystyrene cups fitted with Nitex mesh on two opposing sides. Cups were placed in either plexiglass or glass flow-through channels. Alkyl sulfate solutions were delivered to the troughs via peristaltic pumps at one end and pumped through the individual test chambers in a linear fashion, exiting at the downstream end. Flow-th rough tests we re conducted with both reconstituted and river water. Control mortalit y and reproduction met current U.S. Environmental Protection Agency cr iteria (less than 20% mortality and greater than 15 neonates/female). Three advantages of this system are (1) the method provides an advance over current Ceriodaphnia dubia chronic test methods for sorptive and labile compounds, (2) it is compact and portable, and (3) it is usefu l for other small aquatic organism tests. (C) 1996 by John Wiley & Son s, Inc.